From 4f43e3f854a3cc24d24dd90c9f4185640cc81b31 Mon Sep 17 00:00:00 2001
From: sjplimp <sjplimp@f3b2605a-c512-4ea7-a41b-209d697bcdaa>
Date: Thu, 1 May 2014 17:44:24 +0000
Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@11869
 f3b2605a-c512-4ea7-a41b-209d697bcdaa

---
 src/fix_addforce.cpp | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/fix_addforce.cpp b/src/fix_addforce.cpp
index 66f68715d6..dcac27a012 100644
--- a/src/fix_addforce.cpp
+++ b/src/fix_addforce.cpp
@@ -268,16 +268,24 @@ void FixAddForce::post_force(int vflag)
     modify->clearstep_compute();
 
     if (xstyle == EQUAL) xvalue = input->variable->compute_equal(xvar);
-    else if (xstyle == ATOM && sforce)
-      input->variable->compute_atom(xvar,igroup,&sforce[0][0],4,0);
+    else if (xstyle == ATOM) {
+      if (sforce) input->variable->compute_atom(xvar,igroup,&sforce[0][0],4,0);
+      else input->variable->compute_atom(xvar,igroup,NULL,4,0);
+    }
     if (ystyle == EQUAL) yvalue = input->variable->compute_equal(yvar);
-    else if (ystyle == ATOM && sforce)
-      input->variable->compute_atom(yvar,igroup,&sforce[0][1],4,0);
+    else if (ystyle == ATOM) {
+      if (sforce) input->variable->compute_atom(yvar,igroup,&sforce[0][1],4,0);
+      else input->variable->compute_atom(yvar,igroup,NULL,4,0);
+    }
     if (zstyle == EQUAL) zvalue = input->variable->compute_equal(zvar);
-    else if (zstyle == ATOM && sforce)
-      input->variable->compute_atom(zvar,igroup,&sforce[0][2],4,0);
-    if (estyle == ATOM && sforce)
-      input->variable->compute_atom(evar,igroup,&sforce[0][3],4,0);
+    else if (zstyle == ATOM) {
+      if (sforce) input->variable->compute_atom(zvar,igroup,&sforce[0][2],4,0);
+      else input->variable->compute_atom(zvar,igroup,NULL,4,0);
+    }
+    if (estyle == ATOM) {
+      if (sforce) input->variable->compute_atom(evar,igroup,&sforce[0][3],4,0);
+      else input->variable->compute_atom(evar,igroup,NULL,4,0);
+    }
 
     modify->addstep_compute(update->ntimestep + 1);